To step into; to enter a place. Also used figuratively for entering a new field or area.
彼は深夜の研究室にそっと踏み入った。
He quietly stepped into the laboratory late at night.
初心者がプロの世界に踏み入るのは簡単ではない。
It's not easy for a beginner to enter the professional world.
この問題は慎重に踏み入るべきだ。
We should approach this issue cautiously (literally: step into it carefully).
立ち入り禁止の区域には踏み入らないでください。
Please do not step into the restricted area.